Vapor recovery apparatus and method for oil and gas wells

ABSTRACT

A vapor recovery apparatus has a first vessel forming a column with upper and lower ends. Liquid, such as oil containing gas enters the bottom of the first column and flows op to a liquid outlet Heat is applied to the rising oil, wherein the oil foams. Gas escapes into the upper end. The foam flows into a second column and along a roughened surface. The bubbles in the foam break apart, releasing the gas. The oil flows down the second column to an outlet. A compressor may be used to withdraw the gas and provide hot compressed gas to beat the rising oil in the first column.

FIELD OF THE INVENTION

The present invention relates to vapor recovery systems for wells, oiland gas processing facilities and the accompanying surface storage tanksand related equipment.

BACKGROUND OF THE INVENTION

Liquids, such as erode oil, condensate and water, produced from wellstypically contain gasses such as natural gas and liquid petroleum gas(LPG). Large amounts of oil, condensate and water that are produced arestored in storage tanks, awaiting transport, further processing orrefining. When liquid is stored in a storage tank, gas contained in theliquid can separate or vaporize due to a variety of factors. Forexample, if the liquid experiences a pressure drop, then vapors willflash off. If the liquid level in the storage tank changes, or theliquid is agitated, the gas separates. If the tank is subjected totemperature swings or barometric pressure changes, gas can also separatefrom, the liquid.

Due to environmental and economic reasons, it is desirable to capturethese gasses. Capturing the gasses allows the gas to be sold.Alternatively, the gas can be burned. Venting the gas into theatmosphere is generally frowned upon and in most cases is restricted orrequires permits.

Furthermore, providing liquid with gasses that can. vaporize into astorage tank results in pressure changes inside the tank. As thepressure changes, atmospheric air may he drawn into the storage tank.Oil equipment operators, and in particular pipeline operators, do notwant atmospheric air, with oxygen, introduced into their equipment dueto problems with corrosion.

Thus, it is desirable to put so called “dead” oil without gasses, (andother degassed liquids) into storage tasks. Dead oil does not producegas inside of a storage tank, even when subjected to agitation, pressuredrops, or temperature changes.

In the prior art, various types of equipment exists to separate andcapture gas from liquid before the liquid is provided to a storage tank.One such type of equipment is known as a vapor recovery tower (VRT). Thevapor recovery tower separates the gas from liquid in such a manner soas not to introduce air into the storage tank.

The prior art vapor recovery tower, while removing much of the gas fromthe liquid, is not particularly efficient in that significant quantitiesof gas can still be provided to the liquid flowing into a storage tank.

It is desired to provide a more efficient vapor recovery tower andmethod.

SUMMARY OF THE INVENTION

A vapor recovery apparatus processes liquid produced from a well. Theproduced liquid contains gas. The apparatus comprises inner and outervessels. The inner vessel has a closed lower end, an intermediateportion, a liquid inlet and a liquid outlet. A first liquid path extendsbetween the liquid inlet and the liquid outlet. The inner vessel liquidoutput is vertically above the liquid inlet. The outer vessel has aclosed lower end and a closed upper end, and an interior. The innervessel liquid outlet and inner vessel portions are located in the outervessel interior, the inner vessel liquid outlet communicates with theouter vessel interior. A liquid outlet is located in a lower portion ofthe second vessel. A gas outlet is at the outer vessel upper end. A heatexchanger is located so as to provide heat to liquid located in thefirst liquid path. A second liquid path extends from where the liquidenters the outer vessel from the inner vessel to a liquid level in theouter vessel.

In accordance with one aspect, the inner vessel lower end is locatedexteriorly of the outer vessel.

In accordance with another aspect the liquid inlet is exterior of theouter vessel.

In accordance with still another aspect, the heat exchanger comprises aheat exchanger inlet and a heat exchanger outlet. The heat exchangerinlet and the heat exchanger outlet, are located exteriorly of the outervessel.

In accordance with another aspect, the inner vessel comprises an outersurface located in the outer vessel interior. The second liquid pathcomprises the inner vessel outer surface.

In accordance with another aspect, the loner vessel outer surface isroughened so as to have a larger surface area relative to a smoothsurface.

In accordance with another aspect, the gas outlet is connected to a gaspipe. The gas pipe extends through the outer vessel interior to alocation near the outer vessel bottom end. wherein the gas pipe exitsthe outer vessel.

In accordance with another aspect, the heat exchanger is located insideof the inner vessel, in the first liquid path.

In accordance with another aspect, the apparatus further comprises acompressor. The compressor receives gas from the gas outlet and providescompressed gas to the heat exchanger.

In accordance with, another aspect, the apparatus further comprises aliquid storage tank having an inlet that is connected to the outervessel outlet.

In accordance with another aspect, the storage tank has a first level ofliquid therein. The outer vessel has a second level of liquid that isthe same as the first level of liquid.

In accordance with another aspect, an annulus is between the innervessel intermediate portion and the outer vessel.

A method of recovering gas from liquid produced from a well, comprisesproviding a vessel and forming a first column of the liquid in thevessel, which first column, has a bottom region and a top region. Theliquid is flowed in the first column from the bottom region to the topregion. Heat is applied to the liquid flowing in the first column. Theliquid is allowed to exit the first column and enter a second column inthe vessel. The liquid flows in the second column from a top of thesecond, column toward a bottom of the second column. The gas is allowedto escape the first and second columns of liquid. The liquid iswithdrawn from the vessel from the bottom of the second column. Theescaped gas is collected from the vessel.

In accordance with one aspect, the heated liquid in the top region ofthe first column is foamed.

In accordance with one aspect, the foamed liquid exiting the firstcolumn is passed over a roughened surface so as to break apart bubblesin the foam and allow the gas to escape.

In accordance with another aspect, the escaped gas is collected bywithdrawing the escaped, gas with a compressor, then compressing the gasand passing the compressed gas through a heat exchanger that applies theheat to the liquid flowing in the first column.

In accordance with another aspect, withdrawing the escaped gas with acompressor further comprises monitoring the pressure of the escaped gasand when the pressure exceeds a predetermined threshold, operating thecompressor.

In accordance with another aspect, the step of withdrawing the liquidfrom the bottom of the second column further comprises providing thewithdrawn liquid, to a storage tank.

In accordance with another aspect, the storage tank has a level ofliquid and the second column of liquid has a level which follows theliquid level in the storage tank.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram showing various surface components of a producingoil well, including a vapor recovery tower.

FIG. 2 is a side cross-sectional view of a prior art vapor recoverytower.

FIG. 3 is a side cross-sectional view of the vapor recovery tower of thepresent invention, in accordance with a preferred embodiment.

FIG. 4 is a close up side view of liquid spilling over the top end ofthe inner vessel and traveling down.

FIG. 5 is a side cross-sectional view of the vapor recovery tower, inaccordance with another embodiment

DESCRIPTION OF THE PREFERRED EMBODIMENT

The vapor recovery apparatus and method processes fluid from an oil andgas well. The fluid contains one or more liquid components such as crudeoil, condensate and water. The fluid also contains gasses such asnatural gas and liquid petroleum gas. Many of the gasses easily vaporizeare otherwise volatile. Vapors and volatile compounds are removed fromthe liquid in an efficient manner. The vapors and volatile compounds canbe sold or flared off. The liquid is put into a storage vessel; theliquid is “dead”, with the gasses removed therefrom. Dead liquid instorage vessels minimizes temperature related pressure changes withinthe vessel. Consequently, the admittance of atmospheric air into thestorage vessel is minimized if not eliminated.

In the description of the preferred embodiment, the liquid is oil,although other liquids, such as water or condensate, can be processed.

The liquid flows through the vapor recovery apparatus in a passivemanner. No pumps or agitators are needed.

In FIG. 1, there is shown a producing oil well 11 with various surfaceequipment. Oil flows out of the well into a heater treater 13. Heatertreaters are conventional and are used to process an emulsion of oil andwater. Heat is applied to separate the water from the oil. Some of thegas that may he present is also separated. However, the oil may stillretain gas. The removed water is stored in a water storage tank (actshown) or disposed of in some other fashion. An alternative to a heatertreater is a separator which separates water from the oil. Oil exitingthe separator may still retain gas. Oil exiting the heater treater 13 orseparator is then routed to one or more oil storage tanks 15.Alternatively, the oil may be provided to a pipeline for transport.

Before the oil enters the storage tank 15, it is processed to removevapors or volatile compounds by way of a vapor recovery tower 17. Vaporsleave the upper end of the vapor recovery tower 17 and flow to acompressor 19. In the prior art, the compressed gas leaves thecompressor 19 and flows directly to a sales line 22. However, as will beexplained in more detail below, with the preferred embodiment, thecompressed gas enters the vapor recovery tower.

Oil leaves the vapor recovery tower and flows into the storage tank 15.It is desired for the oil that is entering the storage tank 15 to bedead, or without gasses that can separate from the oil under normalatmospheric conditions.

A prior art vapor recovery tower 18 is shown in FIG. 2. The tower is avertically oriented vessel, typically made of tubular material andhaving capped bottom and top ends. Oil 20 flows from the separator 13 orheater treater to an inlet 21. The oil falls vertically into a pool 23of oil. During the vertical drop, some vapors 24 leave the oil and flowup to a gas outlet 25 and on to the compressor 19 and sales line 22.When the oil contacts the pool 23, it typically still contains gas orvapors. The oil slowly moves to the bottom of the vessel wherein moregas leaves the oil and flows up. When the oil reaches the bottom of thevessel, it flows out of the outlet 27 and into a storage tank 15. Theflow is typically passive so as not to require a pump; as the level ofoil inside the vapor recovery tower is the same as the oil level in thestorage tank. To drop the oil level in the storage tank, or a rise ofoil level in the vapor recovery tower, results in oil flowing out of thevapor recovery tower into the storage tank. The vapor recovery tower 18removes most of the vapor from the oil, without the introduction ofatmospheric air. However, the vapor recovery tower 18 is ill equipped tohandle surges of oil from the oil inlet and some vapor makes its wayinto the storage tank. The oil in the pool 23 sinks to the bottom. Asthe oil sinks, hydrostatic pressure on the oil increases, making gasseparation difficult.

FIG. 3 shows the vapor recovery tower 17 of the present invention, inaccordance with a preferred embodiment. The tower is verticallyoriented. The tower has an inner vessel 31 and an outer vessel 33. Theinner vessel 31 is a tube with a closed bottom end 35, or base plate,and an open top end 37. The bottom end 35 can hear on the ground or on asupport structure. An intermediate portion 38 is located between the twoends 35, 37. An oil, or liquid, inlet 39 is provided near the bottom end35 of the inner vessel 31. A heat exchanger 41 is located in the innervessel between the oil inlet 39 and the top end 37. In the preferredembodiment, the heat exchanger 41 is a coil, through which flowscompressed gas from the compressor 19. There is a compressor gas inlet43 and a gas outlet 45. The islet 43 is located near the bottom end 35.The compressor gas inlet 43 is connected to the output of the compressor19. The gas outlet 45 is connected to the gas sales line 22.

The interior of the inner vessel 31 forms a liquid path that extendsfrom the oil inlet 39, past the heat exchanger 41, to the top end 37.

The outer vessel 33 surrounds and extends above the inner vessel 31. Theouter vessel 33 is a tube of larger inside diameter than the outsidediameter of the inner vessel 31, such that there is an annulus 47between the inner and outer vessels. Supports 77, or alignment plates,exit from the inner vessel radially outward. The supports 77, which arelocated near the top end 37, maintain the inner vessel 31 in aconcentric alignment with the outer vessel 33. The outer vessel has aclosed, or capped bottom, end 49. In the preferred embodiment, thebottom end 49 of the outer vessel is located above the bottom end 35 ofthe inner vessel. This simplifies the inner vessel inlets 39, 43 andoutlet 45. Thus, the annulus 47 is between the outer vessel 33 and theintermediate portion 38 and upper end 37 of the inner vessel 31.However, the inner vessel could be completely contained within the outervessel. The outer vessel has a closed top end 51 located a distanceabove the top end 37 of the inner vessel. A gas outlet 53 is at the topend 51. A pipe 54 extends from the gas outlet 53 to the compressor 19.Near the bottom end 49 of the outer vessel, there is an oil, or liquid,outlet 55 which connects to one or more storage tanks 15. A liquid pathextends from the top end 37 of the inner vessel, through the annulusdown to the oil outlet 55. The outer vessel 33 has tie-off lugs 78located along its length and spaced around the circumference. Thetie-off lugs 78 can be used to secure bracing or cabling to maintain thetower in a vertical orientation. The top end has lifting lugs 79, whichmay be of the pivoting type. The lifting lugs are used duringinstallation of the tower (with a crane). The outer shell also hassensors coupled thereto by ports. The ports provide access to theinterior by the sensors. There may be a temperature sensor SO and apressure sensor 81. The sensors can be manually read, or can send databy cables or wirelessly to other devices.

The compressor 19 has an input that is connected to the pressure sensor81 by way of a controller 82 (see FIG. 1). The controller isprogrammable. When the internal pressure of the tower increases to afirst predetermined pressure, the controller 82 causes the compressor 19to operate. When the internal pressure falls below another, second,predetermined, pressure, the controller causes the compressor to stopoperating. The first predetermined pressure to start operation of thecompressor is selected so as not to interfere with the release of gasfrom oil in the tower. The second predetermined pressure, to cause thecompressor to stop operating, may be less than atmospheric pressure, soas to apply a partial vacuum to the tower interior. Operating thecompressor involves starting and stopping the compressor. As analternative to stopping the compressors the compressor can be idled. Asanother alternative, a bypass can be used, where the gas input to thecompressor is selected from the tower 17 and another source. When thetower pressure increases, the gas input is taken, from the tower. Whenthe tower pressure is low, the gas input into the compressor comes fromthe other source, for example a second vapor recovery tower from anotherwell. Although the pressure sensor 81 is shown in the figures as locatedin the lower portion of the tower, it can he located in the upper part,exposed to gas.

Oil 61 pools in the annulus 47. The top surface, or level 63, of oil inthe annulus is a distance below the top end 37 of the inner vessel. Whenthe oil outlet 55 is connected to a bottom region of the storage tank,the level 63 of oil in the annulus reflects the level of oil in thestorage tank. The height of the top end 37 of the inner vessel islocated above the top end of the storage tank 15. Thus, the level 63 ofoil in the tower can follow the level of oil in the storage tank.

Alternatively, as shown in FIG. 1, the oil outlet 55 is connected to apipe 55A at the top of the storage tank. The pipe is generallyhorizontal and has a top pipe into the storage tank. Oil in the annulus47 in the tower 17 pushes oil out through the outlet 55 and up to thepipe 55A, where it drops into the tank 15. Thus, the oil level 63 in thetower 17 is above the pipe 55A. The pipe 55A can feed oil to a singlestorage tank. Alternatively, the pipe 55A can be a manifold that feedsoil to plural storage tanks.

In operation, oil 60 from the separator or well is introduced into thebottom of the inner vessel 31 by way of the oil inlet 39. This oil 60typically contains gas. The oil in the bottom is displaced upwardly byincoming oil. A column of oil forms in the inner vessel. As the oilrises inside of the column formed by the inner vessel 31, it follows afirst liquid path. The oil is raised in temperature by the heatexchanger 41. The heat exchanger 41 receives hot compressed gas from thecompressor 19 and can increase the temperature of the oil by 20-30degrees F. Furthermore, as the oil rises inside of the inner vessel 31,it is subjected to less and less hydrostatic pressure. The decrease inpressure and the increase in temperature present more favorableconditions to separate the gas from the oil as lowering the pressure andincreasing the temperature lowers the boiling point of the liquids whichflash to gas. The gas 24 bubbles out of the oil. As the gas is separatedfrom the oil the density of the fluid in the upper end portion of theinner vessel 31 decreases, thereby further reducing hydrostatic pressureon the oil and releasing even more gasses. The warm oil rises to the topof the inner vessel, also contributing to the release of gasses throughthe reduction of hydrostatic pressure.

By the time the oil reaches the open top end 37 of the inner vessel 31,the oil is likely foaming because the gasses are separating and leavingthe oil. The gasses travel up inside of the outer vessel to the gasoutlet 53. The gasses then flow to the compressor 19.

The foam 66 spills over the edge of the top end 37 of the inner vessel31 (see FIG. 4). The foam moves along another liquid path, namely byfelling down the outside surface 67 of the inner vessel. As the foam 66travels down the outside surface 67, the bubbles in the foam tend tobreak apart, releasing the gas therein and further separating gas fromthe oil. The outside surface 67 could be smooth. However, in thepreferred embodiment, the outside surface 67 is modified to increase thesurface area. Material can be subtracted from or added to the innervessel to roughen the outside surface. Material can he subtracted fromthe inner vessel, as for example, by sand blasting. Alternatively,material such as expanded metal can be secured (such as by welding) tothe outside surface. The falling oil enters the pool 61 of oil. Thedistance between the top cod 37 of the inner vessel and the top surface63 of the pool in the annulus is sufficient to allow gasses to separatefrom the oil. In the preferred embodiment, the top end 37 is at leastfour feet above the highest top level 63 of oil in the annulus. Thelevel 63 of oil in the annulus typically fluctuates to match the levelof oil in the storage tank 15. Most storage tanks have a maximum oilheight of twenty feet. Thus, the top end 37 for a typical installationis at least twenty four feet high.

If there is any gas left in the oil, the oil is foamy and sits on top ofthe pool until it releases its gas and descends into the pool. Oilfalling along the outside surface 67 and near the top of the pool 61 mayreceive some heat through the wall of the inner vessel 31, which isthermally conductive, being made of steel or some other metal. Thisassists the oil near the top of the pool in releasing any remaining gas.As the oil cools, it descends in the annulus. By the time the oilreaches the outlet 55 in the bottom of the inner vessel the oil is“dead”, without volatile gasses flashing off under normal ambientconditions. Once the oil leaves the inner vessel, it descends in theannular column to the liquid outlet 55.

Unlike the prior art, the vapor recovery tower of the present inventionworks with the temperature and pressure characteristics of fluidcolumns. The prior art vapor recovery tower of FIG. 2 confines theseparation, portions or zones to the distance between the oil inlet 21and pool level 23, when the oil is falling. It is believed that most ofthe gas separation occurs on the fall While some gas may separate whenthe oil is at the top of the pool, as the oil drops down in the pool,the hydrostatic pressure increases and the temperature cools, bothfactors that retard, rather than provide, gas separation.

In contrast, the vapor recovery tower 17 of the present invention flowsthe oil up, not down, in the fluid column in the inner vessel, thususing temperature and pressure to an advantage to separate the gas. Thepressure is decreased and the temperature increased at the top of theinner vessel fluid column. The heat exchanger 41 further increases thetemperature of the oil When the oil is allowed to fall into the othervessel pool or column, it is not a free fall, but slowed by flowingalong the outside surface 67 of the inner vessel. All of these factorscontribute to the separation of gas from the oil.

The dead oil is drawn out of the vapor recovery tower 17 into thestorage tank as with conventional vapor recovery towers 18. As the oillevel in the storage tank fills, it draws oil out of the vapor recoverytower. Alternatively, a rise in oil level in the vapor recover tower canposh oil out of the tower into the storage tank. The level 63 of oil inthe vapor recovery tower follows the oil level in the storage tank.

The vapor recovery tower 17 is sized according to the particularapplication. In general, the oil should be retained in the vaporrecovery tower, whether in the inner vessel or the outer vessel, for asufficient time to separate the gas from the oil. This typically dependson the characteristics of the oil, gas and the well. In general, vaporrecovery towers have retention times of at least thirty minutes, unlessthe particular circumstances require a different retention time. Sizingincludes sizing the inner and outer vessels 31, 33.

The vapor recovery tower 17 is particularly well suited, to surges ofoil produced. If excess oil enters the bottom of the inner vessel 31, itmerely pushes into the foamy upper portion, which can absorb the extravolume of oil. Also, if any foam is spilled over the top end 37 of theinner vessel, it descends along the outside surface 67 where it cancontinue to release gas.

The vapor recovery tower can he provided with sight glasses 65 atvarious heights therein.

The vapor recovery tower uses the heat of the compressed gas for theheat exchanger 41. This is a particularly efficient way of operating theheat exchanger. However, other types of heat exchangers can be used. Forexample, diesel fuel can be burned to create a hot feud which circulatesthrough, the heat exchanger 41. Or any other hot liquid, or gas can beintroduced from various sources an operator may have. Another exampleinvolves using the warm oil and gas directly from the well to flowthrough the heat exchanger, before the oil and gas is processed by aninitial piece of equipment, such as the heater treater 13 or separator.Still another example uses heated fluids, such as oil, from the heatertreater 13, which heated fluids flow through, the heat exchanger 41.

If a compressor is not used, the gas can be stored in other ways orsimply flared off.

FIG. 5 shows a vapor recovery tower 17A in accordance with anotherembodiment. The inner and outer vessels 31, 33 are the same. In thevapor recovery tower 17 of FIG. 3, the gas outlet 53 is located outsideof the tower. With regard to the vapor recovery tower 17A of FIG. 5, thegas outlet 71 in located inside of the tower. The gas outlet 71 is apipe having an inlet 73 at the top end 51 of the tower. The pipe 71extends down along an inside of the outer vessel, entering the annulus47 and then exiting the tower near the bottom at a fitting 75. The exitfitting 75 is located close to ground level. The pipe 54 is coupled tothe fitting 75 and extends to the compressor 19.

The tower 17A of FIG. 5 has several advantages. Installation issimplified and less costly. With the fitting 75 located near groundlevel instead of on top of the tower, personnel can access the fittingwithout an aerial lift to attach the pipe to the compressor. Also,extending the pipe 71 inside the tower maintains the exit gas at ahigher temperature so that the gas is less likely to condense beforeentering the compressor. The pipe 71 is exposed to the highertemperatures of the oil and gas inside the tower. In colderenvironments, maintaining the gas at a higher temperature is anoticeable advantage.

Although the preferred embodiment has been described as having an innerfirst fluid path or column, where the fluid rises, and an outer secondfluid path or column, where the liquid sinks, this could be in someother configuration. For example, the first fluid path or column, couldbe on the outside, surrounding an inner second fluid path or column.Thus, the fluid would rise in the outer fluid path or column and descendin the inner fluid path or column. As another example, the two paths orcolumns need not be concentric, but could be adjacent to one another. Ifthe two columns are adjacent to one another, there could be two towers,side by side. A conduit or channel connects the first column to thesecond, column to allow liquid in the first column to spill over orenter the second column. Gas would either be collected from the upperend of each column, or the gas from one column allowed to flow into theother column, wherein gas could be collected from a single column. Inthis example, the first column or vessel would have an upper vessel endand an upper liquid end; the upper vessel end is above the upper liquidend. Still another example for side by side columns is a single towerwith a vertical partition. The partition divides the tower interior intothe first and second columns, with fluid rising in the first column andspilling over the top end of the partition into the second column. Thefluid level in the second column is below that of the first column. Gasrises to the top of the tower for removal.

The foregoing disclosure and showings made in the drawings are merelyillustrative of the principles of this invention and are not to beinterpreted in a limiting sense.

1. A vapor recovery apparatus for processing liquid produced from awell, the produced liquid containing gas, comprising: a) an inner vesselhaving a lower end, an intermediate portion, a liquid inlet, a liquidoutlet, a first liquid path between the liquid inlet and the liquidoutlet, the inner vessel liquid outlet being vertically above the liquidinlet; b) an outer vessel having a closed lower end and a closed upperend and an interior, the inner vessel liquid, outlet and inner vesselintermediate portion located in the outer vessel interior, the innervessel liquid outlet communicating with the outer vessel interior, anouter vessel liquid outlet located, in a lower portion of the outervessel, a gas outlet at the outer vessel upper end; c) a heat exchangerlocated so as to provide heat to liquid located in the first liquidpath; d) a second liquid path, extending from where the liquid entersthe outer vessel from the inner vessel to a liquid level in the outervessel.
 2. The vapor recovery apparatus of claim 1, wherein the innervessel lower end is located exteriorly of the outer vessel.
 3. The vaporrecovery apparatus of claim 2, wherein the liquid inlet is exterior ofthe outer vessel.
 4. The vapor recovery apparatus of claim 2, whereinthe heat exchanger comprises a heat exchanger inlet and a heat exchangeroutlet, the heat exchanger inlet and the heat exchanger outlet locatedexteriorly of the outer vessel.
 5. The vapor recovery apparatus of claim1, wherein the inner vessel comprises an outer surface located in theouter vessel interior, the second liquid path, comprises the innervessel outer surface.
 6. The vapor recovery apparatus of claim 1,wherein the inner vessel outer surface is roughened so as to have alarger surface area relative to a smooth surface.
 7. The vapor recoveryapparatus of claim 1, wherein the gas outlet is connected to a gas pipe,the gas pipe extending through the outer vessel interior to a locationnear the outer vessel bottom end, wherein, the gas pipe exits the outervessel.
 8. The vapor recovery apparatus of claim 1, wherein the heatexchanger is located inside of the inner vessel, in the first liquidpath.
 9. The vapor recovery apparatus of claim 1, further comprising acompressor, the compressor receiving gas from the gas outlet, thecompressor providing compressed gas to the heat exchanger.
 10. The vaporrecovery apparatus of claim 1, further comprising a liquid storage tankhaving an inlet that is connected to the outer vessel liquid outlet. 11.The vapor recovery apparatus of claim 10, wherein the storage tank has afirst level of liquid therein, the outer vessel has a second level ofliquid that is the same as the first level of liquid.
 12. The vaporrecovery apparatus of claim 1 farther comprising an annulus between theouter vessel and the inner vessel intermediate portion.
 13. A method ofrecovering gas from liquid produced from a well, comprising the stepsof: a) providing a vessel; b) forming a first column of the liquid inthe vessel, the first column having a bottom region and a top region; c)flowing the liquid in the first column from the bottom region to the topregion; d) applying heat to the liquid flowing in the first column; e)allowing the heated liquid to exit the first column and enter a second,column, the second column located in the vessel; f) flowing the liquidin the second column from a top of the second, column toward a. bottomof the second column; g) allowing the gas to escape the first and secondcolumns of liquid; h) withdrawing the liquid from the vessel from thebottom of the second, column; i) collecting the escaped gas from thevessel.
 14. The method of recovering gas from liquid produced from awell of claim 13, further comprising the step of foaming the heatedliquid in the top region of tire first column.
 15. The method ofrecovering gas from liquid produced from a well of claim 14, furthercomprising the step of passing the foamed liquid exiting the firstcolumn over a roughened surface so as to break apart bubbles in the foamand allow the gas to escape.
 16. The method of recovering gas fromliquid produced from a well of claim 13, wherein the step of collectingthe escaped gas farther comprises the step of withdrawing the escapedgas with a compressor, compressing the gas and passing the compressedgas through a heat exchanger that applies the heat to the liquid flowingin the first column.
 17. The method of recovering gas from liquidproduced from a well of claim 16, wherein the step of withdrawing theescaped gas with a compressor further comprises the steps of: a)monitoring the pressure of the escaped gas; b) when the pressure exceedsa predetermined threshold, operating the compressor.
 18. The method ofrecovering gas from liquid produced from a well of claim 13, wherein thestep of withdrawing the liquid from the bottom of the second columnfurther comprises the step of providing the withdrawn liquid to astorage tank.
 19. The method of recovering gas from liquid produced froma well of claim 18, wherein the storage tank has a level of liquid andthe second column has a level of liquid that follows the storage tanklevel of liquid.